What Is the Minimum and Maximum Acceleration for a Block on an Inclined Wedge?

[americanforest]

Homework Statement

A block rests on a wedge inclined at an angle \theta. The coefficient of friction between the block and the plane is \mu.Let the wedge move with horizontal acceleration a to the right. Assuming
that tan tan(\theta) < \mu, find the minimum value of a for the block to remain on the wedge without sliding.

Also find the maximum value of a.

Homework Equations

The Attempt at a Solution

mgcos(\theta)+masin(\theta)=F_{normal};<br /> \tex{mgcos(\theta)+\mu (F_{normal})=macos(\theta);<br /> <br /> a=\frac{g(sin+\mu cos}{cos - \mu sin}

which gives wacky limiting values and isn't a range at all but just one value.

 

[hikaru1221]

Have a bit correction with this one: F_{static friction} \leq \mu F_{normal}
Also, there must be a condition for a to be positive, as a acts to the right.